1. Lab 3 Intro to Robots

2. Basic Robot Brain • Programs consist of import lines, function definitions and and a starting point. Line 1: from myro import * Line 2: initialize("comX") Line 3: <any other imports> Line 4: <function definitions> Line 5: def main(): Line 6: <do something> Line 7: <do something> Line 8: ... Line 9: main() Always start from a function called main() Intro to Robots

3. Exercise • Combine the following functions into a program that yoyos and wiggles for a bit. Try to make your dance short and sweet. def yoyo(speed, waitTime): forward(speed, waitTime) backward(speed, waitTime) stop() def wiggle(speed, waitTime): motors(-speed, speed) wait(waitTime) motors(speed, -speed) wait(waitTime) stop() Intro to Robots

4. Exercise: • Take the previous program and rename the main() function dance(). • Now create a main() function that calls dance(). • The problem is if you want to “dance all night”. • Call the program dance.py. • It works but not very interesting: def main(): dance() dance() dance() dance() . . . Intro to Robots

5. Repetition in Python (and other languages): • Programming languages have syntax for repeating the same thing over and over and over and over . . . • for-loop: when you know exactly how many times to repeat something • while-loop: when you don’t know, in advance, exactly how many times you need to repeat something def main(): for i in range(1): dance() keeps calling dance()until 10 seconds havepassed def main(): while timeRemaining(10): dance() Intro to Robots

6. Exercise: • Modify the dance.py program to use a for-loop. Intro to Robots

7. While-Loops: • c(i) is a boolean condition that is True of False depending on the value of i. • f() gives a new value to i, once for each iteration through the loop. • This loop will go on forever if f() never returns a value for which c(i) == False. i = 0 while c(i): # do something i = f() answer = ‘No’while answer == ‘No’: dance() answer = ask(‘Again?’) what happens if you never enter ‘No’but rather ‘no’, ‘n’, NO’, etc. Intro to Robots

8. Infinite Loops: • The example on the last slide shows that a loop can, by accident, go on forever. You can also intentionally write an infinite loop. • How do you stop this loop? while True: # do something Ctrl-C Intro to Robots

9. Exercise: • Modify the dance.py program to replace the for-loop with a while-loop. • Try various while-loops including an infinite loop. Intro to Robots